International Journal of Computer and Communication Engineering, Vol. 3, No. 5, September 2014
Quad Band Rectangular Microstrip Antenna for S and
C-Band Applications
Ambresh P. A., A. A. Sujata, A. M. Khan, P. M. Hadalgi, and P. V. Hunagund

cost glass epoxy substrate material of thickness h=0.16 cm
and permittivity є = 4.4. Fig. 1 shows the geometry of
conventional rectangular microstrip antenna (CRMA) which
is designed for the resonant frequency of 3.5 GHz, using the
equations available in the literature [1]. The substrate area of
the CRMA is A=M×N. The antenna is fed by using
microstripline feeding. This feeding has been selected
because of its simplicity and it can be simultaneously
fabricated along with the antenna element. Fig. 1 consists of a
radiating patch of length and width (L × W) of the patch are
(18.99×26.92), quarter wave transformer of length Lt and
width Wt used between the patch and 50  microstripline feed
of length Lf and width Wf.. At the tip of microstripline feed, a
50  coaxial SMA connector is used for feeding the
microwave power.
Abstract—This paper presents the study of two rhombus
shape slot loaded rectangular microstrip antenna for quad band
operation. The quad bands are achieved at S and C band of
frequencies. Effect of slot embedded on the patch is studied
experimentally for enhancing the bandwidth. It is found that by
using two rhombus shape slots on the patch element with copper
as ground plane, the bandwidth at C-band is enhanced from
2.06 % to 20.4 % without much affecting the operating
bandwidth at C-band. Further enhancement of bandwidth at the
C-band does not affect the nature of broadside radiation
characteristics. Details of antenna design are described and
experimental results are discussed. The proposed antennas may
find applications for the systems operating at S and C-bands.
Index Terms—Microstrip antenna, quad band, rhombus,
VNA, bandwidth.
I. INTRODUCTION
The microstrip antennas (MSAs) are the most widely used
for the last few years due to their attractive features such as
light weight, low volume, ease in fabrication and low cost [1].
However, the major disadvantage associated with MSAs is
their narrow bandwidth [1]-[2] which restricts their many
useful applications. Numbers of studies have been reported in
the literature for enhancing the bandwidth [3]-[6]. Further, the
dual frequency patch antennas have gained wide attention in
radar communication particularly in synthetic aperture radar
(SAR), as they avoid the use of two separate antennas for
transmit and receive applications. Variety of methods have
been proposed to obtain dual band operation, such as by
loading slits [7], using slots in the patch [8], loading the patch
with shorting pins [9], using stacked patches [10] et al. But
the antenna operating at more than two different bands of
frequencies and their enhancement are found rare in the
literature. Hence a simple patch with rhombus shape slot
technique has been used in this study for constructing the
proposed antennas useful for S and C band applications.
Fig. 1. Geometry of CRMA.
Fig. 2. Geometry of TRSRMSA.
Fig. 2 shows the geometry of two rhombus shape slot
rectangular antenna (TRSRMSA). The dimension of
TRSRMSA shown in Fig. 2 remains same as that of
rectangular patch and feed line as shown in Fig. 1, but two
rhombus shaped slot which are placed horizontal on patch are
etched on the patch plane of CRMA as shown in Fig. 2. Hence,
this antenna is named as two rhombus shape slot rectangular
antenna (TRSRMSA). The dimensions of all the slots are
taken in terms of λ0, where λ0 is the free space wavelength
corresponding to the designed frequency of conventional
RMA i.e. 3.5 GHz. The length and width (L ×W) of the patch
are (18.99×26.92). The side length x is 6.8 mm. The
horizontal and vertical slot lengths (L1 and L2) slots are 9.6
mm and 13.5 mm.
II. DESCRIPTION OF ANTENNA GEOMETRY
The art work of the proposed antennas are developed using
computer software AutoCAD-2012 and are fabricated on low
Manuscript received January 20, 2014; revised April 25, 2014.
Ambresh P. A. and A. M. Khan are with the Dept. of Electronics,
Mangalore University, Mangalore 574199, Karnataka, India (e-mail:
[email protected]).
A. A. Sujata is with the Dept. of Electronics, Godutai Engineering
College for Women, Gulbarga. Karnataka, India.
P. M. Hadalgi and P. V. Hunagund is with the Microwave Research
Laboratory, Department of Applied Electronics, Gulbarga University,
Gulbarga-585106, Karnataka, India.
DOI: 10.7763/IJCCE.2014.V3.345
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International Journal of Computer and Communication Engineering, Vol. 3, No. 5, September 2014
III. EXPERIMENTAL RESULTS
The S-parameters of passive and active networks can be
measured with a vector network analyzer (VNA), which is a
two (or four) channel microwave receiver designed to process
the magnitude and phase of the transmitted and reflected
waves from the network. It compares the incident signal that
leaves the analyzer with either the signal that is transmitted
through the test device or the signal that is reflected from its
input. The results of return loss, VSWR and impedance
presented in this thesis are taken on VNA (Rohde & Schwarz,
Germany make, ZVK model 1127.8651, 10 MHz-40 GHZ).
The impedance bandwidth over return loss less than -10 dB
for the proposed antennas is measured at S and C band of
microwave frequencies. The variation of return loss versus
frequency of CRMA is as shown in Fig. 3. From the figure it is
clear that, the antenna resonates at fr1 = 3.6 GHz of frequency
which is very much close to the designed frequency of 3.5
GHz and hence validates the design. From this graph, the
experimental impedance bandwidth is calculated using the
formula,
 fH  fL 
  100%
fC


BW = 
Fig. 4. Variation of return loss Vs frequency of TRSRMSA.
Hence the construction of TRSRMSA does not affect the
basic resonant property of antenna that is the primary band
BW1 which lies at S-band but gives other three bands BW2,
BW3 and BW4 at C-band. However, it is seen that the resonant
frequency fr2 of TRSRMSA in the primary band shifts to 4.64
GHz, when compared to resonant frequency fr1 of CRMA i.e.
2.63 GHz in BW1. The shift of resonant frequency is mainly
due to feed used in TRSRMSA. The dual bands are due to
independent resonance of patch and slot elements in
TRSRMSA. Hence it is clear that, TRSRMSA is quite
effective in enhancing the bandwidth of antenna at S, C-band
retaining the resonant property of antenna.
(1)
where, fH and fL are the upper and lower cut-off frequency of
the band respectively when its return loss becomes -10dB and
fc is the center frequency between fH and fL.. Hence by using (1)
the bandwidth BW1 of CRMA is found to be 2.06 %. The
theoretical bandwidth of this antenna is calculated using [2],
 Ah
B andw idth  %  = 
  0  r



W
(2)
L
where, A is the correction factor, which is found to be 180 as
per [11]. The theoretical bandwidth of CRMA is found to be
3.42 %, which is in good agreement with the experimental
value. Fig. 4 shows the variation of return loss versus
frequency of TRSRMSA. The antenna resonates for four band
of frequencies, fr1=2.63 GHz, fr2 = 4.64 GHz, fr3 =5.94 GHz
and fr4 = 7.78 GHz. The respective bandwidths at fr1, fr2, fr3
and fr4 are 1.52 %, 1.07 %, 2.02 % and 20.4 %. It is clear that
the BW1 lies in the S-band (2-4 GHz), where as BW2, BW3
and BW4 lies in the C-band (4-8 GHz).
Fig. 5. PC based radiation pattern measurement setup.
The radiation patterns for CRMA and TRSRMSA are
measured using basic microwave measurement setup and
position control system (S310C) and antenna positioner
(S310P) as shown in Fig. 5. Fig. 6 and Fig. 7 show the
co-polar and cross-polar radiation patterns of CRMA and
TRSRMSA, which are measured at their respective resonant
bands. From these figures, it is clear that the patterns are
broadsided and linearly polarized. The quad band operation
and enhancement of bandwidth does not affect the nature of
broadside radiation characteristics. For the calculation of gain
of antenna under test (AUT), the power transmitted „Pt‟ by
pyramidal horn antenna and power received „Pr‟ by AUT are
Fig. 3. Variation of return loss Vs frequency of conventional RMSA.
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International Journal of Computer and Communication Engineering, Vol. 3, No. 5, September 2014
where, λ0 is the operating wavelength in cm and R is the
distance between the transmitting and receiving antenna. The
gain of CRMA is found to be 2.3 dB. The gains of TRSRMSA
is measured for all resonant frequencies and are found to be
2.6 dB, 3.1 dB, 3.8dB and 6.3dB respectively. The maximum
gain is found to be 6.3 dB for 7.78 GHz. The proposed
TRSRMSA finds application in S and C frequency band of
wireless communication.
The logical variables used at the microwave frequency are
traveling waves rather than total voltage and total currents.
The basic task of vector network analyzer (VNA) is the
measurement of S-parameters. The photography of VNA is as
shown in Fig. 8.
measured independently [11]. With the help of these
experimental data, the maximum gain G (dB) of CRMA in
BW1 is calculated using (3).
 Pr 
 0 
 dB
 - ( G t ) d B - 2 0 lo g 
 4 R 
 Pt 
( G ) d B  1 0 lo g 
(3)
Fig. 6. Measured radiation pattern of CRMA measured at 3.8 GHz.
(a) fr1=2.63GHz
Fig. 8. The photography of vector network analyzer (VNA).
IV. CONCLUSION
This paper presents the study, design of quad band
operation of antenna at four different bands of frequencies
which is possible by constructing two rhombus slots on
rectangular microstrip patch element. Effect of rhombus slot
of different shapes has been studied experimentally for
enhancing the bandwidth. It is found that, the bandwidth at the
C-band is enhanced to 20.4 % without much affecting the
primary band. The enhancement of bandwidth at S, C-band
does not affect the nature of broadside radiation
characteristics. The proposed antennas are simple in their
design and construction and they use low cost substrate
material. These antennas may find applications for the
systems operating at S and C-band of frequencies.
(b) fr2 = 4.64GHz
ACKNOWLEDGMENT
Authors would like to express gratitude to The Department
of Science and Technology (DST), Government of India,
New Delhi, for sanctioning Vector Network Analyzer to this
Department under FIST Project
(c) fr3 =5.94GHz
REFERENCES
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[2]
[3]
[4]
(d) fr4 = 7.78 GHz
Fig. 7. Measured radiation patterns of TRSRMSA.
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A. A. Sujata received M.Tech degree in communication systems
engineering from Poojya Doddappa Appa College of Engineering, Gulbarga,
Karnataka. Since 7 years ago, she is working as an Asst. Prof in the Dept. of
Electronics, Godutai Engineering College for Women, Gulbarga. Her
research interests are communication systems, image processing. She has
published 6 papers in referred journals and conference proceedings.
Ambresh P. A. received the M.Tech degree in
communication systems engineering from Poojya
Doddappa Appa College of Engineering, Gulbarga,
Karanataka in the year of 2008. In April 2013, he also
received Ph.D degree in the field of microwave
electronics in the Department of P. G. Studies &
Research in Applied Electronics, Gulbarga University,
Gulbarga, Karnataka. Currently, he is working as an
Asst. Prof. in the Dept. of Electronics, Mangalore
University, Mangalore. India. His research interest involves design,
development and parametric performance study of microstrip antenna for
RF/Microwave front-ends. He has published more than 40 papers in referred
journals and conference proceedings. He is also researching antenna design
for GPS/IMT-2000/WLAN/WiMax application.
P. M. Hadalgi received the M.Sc and Ph.D degrees in
the Department of P. G. Studies & Research in
Applied Electronics, Gulbarga University, Gulbarga in
the year 1981 and 2006 respectively. From 1985 to
2001, he was a lecturer in the Department of Applied
Electronics, Gulbarga University, Gulbarga. From
2001 to 2006, he was a Sr. Sc. lecturer in Dept. of
Applied Electronics Gulbarga University, Gulbarga.
Recently he has been promoted as associate professor
and chairman in the Department of Applied Electronics, Gulbarga
University, Gulbarga. He had published more than 150 papers in referred
journals and conference proceedings. His main research interest includes
study, design and implementation of microwave antennas and front-end
systems for UWB, WiMax, RADAR and mobile telecommunication
systems.
[5]
P. V. Hunagund received his M.Sc in Department of
Applied Electronics, Gulbarga University, Gulbarga in
1981. In the year of 1992, he received Ph.D degree
from Gulbarga University, Gulbarga. From 1984 to
1993, he was a lecturer in the Department of Applied
Electronics, Gulbarga University, Gulbarga. From
1993 to 2003, he was a reader in Dept. of Applied
Electronics, Gulbarga University, Gulbarga. In 2003
he got promoted under CAS as a professor. He has
served as chairman of the department three times successfully. 6 Ph.D
students have got their Ph.D degree under his guidance and 6 more are still
working on it. He had published more than 200 papers in referred journals
and conference proceedings.
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